1. Field of the Invention
This invention relates generally to flow control devices, including liquid and gaseous flow control, and more specifically to a new and improved method and apparatus for controlling the flow of liquids into, and gases out of, liquid storage receptacles.
2. Prior Art and Other Considerations
Liquid storage receptacles, particularly large, mobile, unvented tanks such as are commonly used in industry to store and transport liquid fuels and other liquid chemicals are typically refilled from pressurized sources, either in the field or at various refilling locations or stations. Permanent storage receptacles, depending on their location, may be refilled using non-pressurized or gravity feed means.
In both systems, the storage receptacle must be vented in some way during the refilling process to allow internal vapor or air to escape the receptacle as the liquid level in the tank rises. Presently, venting is typically accomplished by independent, permanently installed, venting mechanisms such as manually operated bleed valves. During the refilling process it is advantageous to provide a shut-off mechanism which will prevent overfilling the storage receptacle and thus avoid spillage or leakage of the fuel or other chemical being stored. Prior art devices, such as those disclosed by U.S. Pat. No. 5,027,870 to Butterfield and U.S. Pat. No. 3,563,263 to Benson disclose two general methods of flow control for liquid storage tanks which have been used or attempted in the past.
The Butterfield device utilizes the rising level of liquid within a storage receptacle to activate a dual float system to close a primary or main valve and then a secondary or bleed vane which, in combination, work to stop the flow of liquid into the receptacle. The Butterfield device appears to be designed for low flow or gravity feed systems and would fail to stop the flow of liquid in a pressurized system. Also, there is no provision or mechanism within the device, or otherwise, for venting vapor during the refilling process.
The Benson device, on the other hand, uses a bulb-type float mechanism which is designed to close off the "vent" line of a typical underground storage tank as the level of liquid within the tank rises to a predetermined level. Rising pressure within the tank, upon closure of the vent valve, prevents further introduction of liquid into the tank from the refilling source. The Benson device is not designed to stop the flow of liquid at all and, as with the Butterfield device, would fail to stop the flow of liquid in a pressurized system.
Prior art devices and methods such as those discussed herein, and other similar devices, while perhaps functionally adequate for their designed purpose, are nevertheless generally quite complex in their construction, design and operation, and typically require many moving parts to accomplish their intended function. Many of the prior art devices designed to date are difficult to install and once installed, require periodic adjustments or require the device to be manually reset once its valving mechanism has been triggered. In others, the design is restrictive thereby preventing the use of the device in situations where the flow rate is high or the liquid is pressurized. Other problems with the prior art include the inability to provide a means for the recovery of vapor, if desired, and the inability of the device to effectively operate in an inclined or off-center position such as is typically encountered in the field where tankers or heavy equipment may be resting on unlevel ground or otherwise oriented in a tilted or off-center position.
It would be expedient, therefore, for the provision of a simplified, self-contained, method and apparatus for the automatic control of liquid flowing into storage receptacles and which also provides for the safe and effective release of vapor during the refilling process. It would also be expedient for said device to be quickly and easily installed or removed, to be extremely durable and to be able to operate under high pressure and high flow rates and in off-center positions typically encountered in the field.